For a power measurement at a circuit breaker, for example for an energy consumption analysis, a voltage tap is required. Up until now, an external device outside the circuit breaker was used for this purpose. In order to be able to perform the power measurement inside the breaker itself, an internal voltage tap inside the breaker is also necessary. A circuit breaker is known from document US 2009/0190289 A1 wherein a voltage tap is incorporated into the circuit breaker itself, so that an external module can be dispensed with. Tapping such a high voltage as that present in a primary line of a circuit breaker requires a reduction in the voltage with the help of voltage dividers to a value tolerable by electronic measurement gear. Carrying the high-voltage signal over traces, lines, adapters and contacts brings about problems due to fouling, high temperatures, possible leakage paths and disruptive influences on the electronics due to electrical or electromagnetic effects. Moreover, there is the problem of providing sufficient space for additional elements inside a breaker housing.